| Under the trend of "urbanization",the development of foundation pit engineering gradually towards to the deeper,larger,higher technical content,bigger construction difficulty,and often excavation in the dense buildings,affected by site location,surrounding and underground environment,outside the foundation pit excavation scope do not have enough space to put slope,here are strict requirements for the stability and displacement control of foundation pit.Therefore,it is necessary to adopt reasonable excavation and support system to ensure the stability of the foundation pit.This paper first introduces the force and action mechanism of the deep foundation pit support system,introduces the actual working condition and monitoring scheme of a foundation pit project in xi ’an,and after excavation the deformation of the top and surrounding buildings of the foundation pit are analyzed.When the numerical simulation method is used to treat the foundation pit,the first practical foundation pit engineering represents the excavation supporting numerical research on the EF,then analyze the stability of foundation pit in the process and optimize the supporting parameters,finally in foundation pit overall for object,to the whole foundation pit excavation is analyzed and the horizontal displacement of side direction changes,at the same time demonstrate the validity of the optimizing the EF supporting scheme,provide numerical analysis theory for the future similar projects.The main research contents and conclusions of this paper are as follows:(1)through the study and analysis of the field deformation monitoring data,it can be found that the supporting method,the surrounding buildings and the time effect all affect the deformation stability of the foundation pit;Comparing between the monitoring results and the warning values,and the results shows that the foundation pit is stable.(2)The EF section of deep foundation pit was selected and the excavation simulation was carried out with Flac3 D software.The retaining pile effectively blocks the vertical stress of soil,the tension of anchor cable effectively offsets the active pressure of soil,and the pile crown beam plays a certain role in limiting the horizontal deformation of retaining pile.It is shown that the supporting structure formed by retaining pile,pile crown beam and anchor cable plays a decisive role in the stability of each stage of foundation pit excavation.(3)When the relevant support parameters of EF section of foundation pit are optimized,the anchorage cable prestress and the length of retaining pile have great influence on the deformation of foundation pit,while the pile diameter and the upper load of surrounding buildings have a smaller impact.At the same time,the effectiveness of Flac3 D in simulating foundation pit engineering and its supporting system is verified,which provides an important reference for the design,construction and research of deep foundation pit supporting engineering.(4)the horizontal displacement of pit retaining pile and retaining wall the top beam and pile is within the scope of control in length direction of the foundation,from the excavation process,the maximum horizontal displacement of retaining piles along with the excavation and down trends,which shows anchor cable horizontal displacement play an important role in limiting retaining pile,slope protection pile plus anchor cable has good applicability for the foundation pit supporting type.The horizontal displacement of retaining pile,retaining wall and pile crown beam in the direction of width of foundation pit is smaller than that in the direction of length and has better stability.The soil heave of the foundation pit is within 20 mm,and the overall stability of the foundation pit is better. |
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